The spread of smartphones and the like increases mobile traffic. In order to handle the increased traffic, the configuration is discussed to arrange many cells (hereinafter, sometimes referred to as a “small cells”) in which less power is transmitted than in the macro cells in the past. Arranging a plurality of small cells, which use an identical frequency, allows for the handling of a larger amount of traffic by geographically reusing the radio resources. As a method for arranging the small cells, the configuration referred to as a Centralized Radio Access Network (C-RAN) is sometimes used. In the C-RAN, a radio resource scheduler and a signal processor are centralized in one or several places while a radio transmitter and a plurality of Remote Radio Heads (RRHs) having an antenna function are decentralized and arranged. The RRH is referred to as a transmission point hereinafter.
Patent Literature 1 Japanese Laid-open Patent Application No. 2015-61248
Patent Literature 2 Japanese National Publication of International Patent Application No. 2014-505447
The more the transmission points are arranged, the lager the amount of traffic can be handled. On the other hand, the more the transmission points are arranged, the larger the interference between the transmission points is adversely.